1. Field of the Invention
This invention generally relates to a rolling-contact bearing, and, in particular to a retainer for use in a linear motion rolling-contact bearing for allowing a slider assembly to move along an unlimited length of a guide rail and its manufacturing method.
2. Background of the Invention
A linear motion rolling-contact bearing is well known in the art. This bearing is provided between a straight guide rail and a slider assembly which straddles the guide rail so as to allow the slider assembly to move along the guide rail however long it may be. Such a bearing typically comprises an endless passage in the form of a closed loop defined between the guide rail and the slider assembly and rolling members arranged in the passage, whereby the rolling members roll along the passage as the slider assembly moves along the guide rail so that the silder assembly may move unlimitedly no matter how long the guide rail may be.
The endless passage generally includes a load passage section which runs straight and which is defined by opposed guide grooves provided on the opposed surfaces of the slider assembly and the guide rail, a return passage section which runs generally in parallel with the load passage section, and a pair of connecting passage sections each of which connects the corresponding ends of the load and return passage sections, thereby allowing the rolling members to move along the passage in one direction when the slider moves in the other direction. The rolling members are typically spheres or cylindrical rollers. The bearing also includes a retainer which is typically provided in the load passage section of the endless passage so as to retain the rolling members properly in position and to guide the movement of the rolling members entering into and exiting from the load passage section.
FIG. 2 shows schematically in cross section the structure of the load passage section of such a linear motion rolling-contact bearing employing balls as rolling members. As shown, defined between a slider assembly 3 and a rail 4 is the load passage section in which a ball 1 having a diameter Da is present in rolling contact with the slider assembly 3 and the rail 4. Mounted on the slider assembly 3 is a retainer 2 which has a pair of flange portions which are formed by bending the end portions away from the slider assembly 3 toward the rail 4. The flange portions come closer toward their tip ends where there is defined a distance C between the tip ends of the flange portions, which is smaller than the diameter Da of the ball 1. With this structure, the retainer 2 can retain the ball 1 at the side of the slider assembly 3.
It is to be noted, however, that the flange portions must be formed to have a substantial height so as to secure a sufficient retaining distance which is defined by Da - C. The provision of such high flange portions between the slider assembly 3 and the rail 4 is not advantageous because the grooves formed in the opposed surfaces of the slider assembly 3 and the rail 4 for defining the load passage section tend to be shallow.